Charge Transfer at the TiO2/N3/Ag Interface Monitored by Surface-Enhanced Raman Spectroscopy

The interface of semiconductor–dye–metal system is a crucial issue for investigating dye-sensitized solar cells (DSSCs), where the electron transfer takes place. In this work, a series of assemblies of TiO2/N3 (cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II)) and TiO2/N3/Ag have been fabricated, which were employed for the investigation of the adsorption configuration and conformational change of N3 molecules. We plot degree of charge transfer (CT) (ρCT) as a function of excitation wavelength of TiO2/N3 and TiO2/N3/Ag assemblies, which contributes to the understanding of the CT process in the series of N3 assemblies. According to the variation tendency of ρCT, when laser energy exceeds the CT energy threshold 2.071 eV, ρCT shows an obvious increasing trend with the increasing laser energy. In the case of TiO2/N3/Ag assembly, when the laser energy exceeds the CT energy threshold 1.877 eV, ρCT becomes lager with the increase in the laser energy, until asymptotic behavior appears u...